摘自ORACLE数据库在线！

[@more@]rman 的备份文件，只能在 server 端生成，不管 rman 在什么客户端；（比如 server linux, 而 rman 在 windows 下启动，最终的
backup piece 还是在 linux 端生成）

backup database 的时候，假如不设置 channel 的 limit ，一开始就会创建一个大文件，因此，假如你空间不够，他就会报错，比如
：

RMAN> run { allocate channel c3 type disk; backup database ;}

RMAN-03022: compiling command: allocate
RMAN-03023: executing command: allocate
RMAN-08030: allocated channel: c3
RMAN-08500: channel c3: sid=23 devtype=DISK

RMAN-03022: compiling command: backup
RMAN-03023: executing command: backup
RMAN-08008: channel c3: starting full datafile backupset
RMAN-08502: set_count=19 set_stamp=483979175 creation_time=22-JAN-03
RMAN-08010: channel c3: specifying datafile(s) in backupset
RMAN-08522: input datafile fno=00005 name=/db/oracle/oradata/netbar/users01.dbf
RMAN-08522: input datafile fno=00003 name=/db/oracle/oradata/netbar/rbs01.dbf
RMAN-08522: input datafile fno=00004 name=/db/oracle/oradata/netbar/temp01.dbf
RMAN-08522: input datafile fno=00006 name=/db/oracle/oradata/netbar/indx01.dbf
RMAN-08522: input datafile fno=00001 name=/db/oracle/oradata/netbar/system01.dbf
RMAN-08011: including current controlfile in backupset
RMAN-08522: input datafile fno=00002 name=/db/oracle/oradata/netbar/tools01.dbf
RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-03007: retryable error occurred during execution of command: backup
RMAN-07004: unhandled exception during command execution on channel c3
RMAN-10035: exception raised in RPC: ORA-19504: failed to create file "0jedhrt7_1_1"
ORA-27044: unable to write the header block of file
Linux Error: 22: Invalid argument
Additional information: 2
RMAN-10031: ORA-19624 occurred during call to DBMS_BACKUP_RESTORE.BACKUPPIECECREATE

因此，必须设置 channel 的 limit 啦
RMAN>run { allocate channel c3 type disk;set limit channel c3 kbytes 1800000;backup database format '/home/ora/netbars_%p.rman';}
就完全工作正常。

另外，假如没有指明 format ，那么 文件位置在 $ORACLE_HOME/dbs 下面

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